In the field of endodontics, one of the most important and delicate procedures is that of cleaning or extirpating a root canal to provide a properly dimensioned cavity while essentially maintaining the central axis of the canal. This step is important in order to enable complete filling of the canal without any voids and in a manner which prevents the entrapment of noxious tissue in the canal as the canal is being filled.
In a root canal procedure, the dentist removes inflamed tissue and debris from the canal prior to filling the canal with an inert filling material. In performing this procedure the dentist must gain access to the entire canal, shaping it as necessary. But root canals normally are very small in diameter, and they can often be quite curved. It is therefore very difficult to gain access to the full length of a root canal.
Many tools have been designed to perform the difficult task of cleaning and shaping root canals. Historically, dentists have used a wide multitude of tools to remove the soft and hard tissues of the root canal. These tools, usually called endodontic files, have been made by three basic processes. In one process, a file is created by twisting a prismatic rod of either square or triangular cross section in order to create a file with helical cutting/abrading edges (“K-file”). The second process involves grinding helical flutes into a circular or tapered rod to create a file with one or more helical cutting edges (“Hedstrom file”). The third method involves “hacking” or rapidly striking a circular or tapered rod with a blade at a given angle along the length of the rod, thus creating an endodontic file characterized by a plurality of burr-like barbs or cutting edge projections (“barbed file” or “broach”). Each of these instruments and manufacturing processes has unique advantages, and disadvantages.
A particularly problematic aspect of current state-of-the-art endodontic files, particularly K-files and Hedstrom files, is catastrophic failure caused by torque overload. Often, files will become lodged or jammed within the canal such that continued twisting or turning can cause the file to fail or break off in the canal. For endodontic files having twisting or helically spiraling cutting edges, such files can often unexpectedly engage or borough into the root canal, inadvertently driving the instrument deep into the root canal and possibly puncturing the apical seal thereof and/or otherwise transporting through the canal wall (so-called “screwing-in effect”). Another prevalent problem is heavy torque loading caused by inefficient cutting and/or high surface area engagement of the file with the inner canal wall. Excessive torque loading is problematic because it increases the friction heat generated within the canal per file revolution, increasing the chance of bone necrosis and/or catastrophic failure of the file/reamer instrument.
Accordingly, there is a need for an improved endodontic file design which overcomes these and other problems